Lead Frame Convexo-Concave Structure for Resin Adhesion
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Solution Overview
Problem
Existing semiconductor devices face adhesion issues between lead frames and resin due to insufficient surface area of bumpy portions formed on the lead frames, which can lead to delamination, especially when silver plating is applied, as the bumpy portions are finely formed and filled by the plating film, reducing the surface area and adhesion.
Innovation Solution
A semiconductor device with a high density convexo-concave portion on the lead frame surface, featuring concave portions with diameters between 0.020 mm and 0.060 mm and an S ratio greater than or equal to 1.7, increasing the surface area and enhancing adhesion with resin, while maintaining the S ratio even after silver plating or other metal film formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bumpy portions are formed by chemically roughing the surface of the lead frame, then adhesion between lead frame and resin is improved, but the surface area is not large enough to obtain the expected adhesion
Solution Approach 1:
The surface is segmented into multiple convexo-concave portions with specific dimensional parameters (diameter 0.020-0.060mm, S ratio ≥1.7) rather than using a continuous rough surface. This segmentation creates discrete adhesion zones that collectively provide sufficient total surface area while maintaining effective stress distribution.
Solution Approach 2:
The invention changes the parameters of surface modification from chemical roughing (which creates fine, low-area bumps) to mechanical or photoetching methods that create convexo-concave portions with controlled diameter (0.020-0.060mm) and depth, achieving S ratio ≥1.7. This parameter change increases surface area while maintaining adhesion effectiveness.
2Reliability
If a silver plating film is formed on the bumpy portion, then the lead frame is protected and conductivity is improved, but the bumpy portion is filled by the silver plating film and the surface area decreases
Solution Approach 1:
The convexo-concave portions are formed with predetermined dimensions (diameter 0.020-0.060mm, depth 0.003-0.015mm) before plating, ensuring that even after silver plating fills部分 of the concave areas, sufficient surface area remains. The preliminary structuring accounts for the space-occupying effect of the plating film.
Solution Approach 2:
The invention transitions from two-dimensional surface roughing to three-dimensional convexo-concave structuring with controlled depth (0.003-0.015mm). This dimensional change allows the surface to maintain effective area even when partially filled by plating, as the vertical dimension provides reserve adhesion capacity.
3Reliability
If the surface area of the lead frame is increased to improve adhesion, then delamination is prevented, but the manufacturing complexity increases
Solution Approach 1:
The invention replaces complex mechanical surface treatment methods with photoetching or molding techniques that can create convexo-concave portions in a single step during lead frame fabrication. This substitution maintains manufacturing simplicity while achieving the required S ratio ≥1.7 through precise dimensional control.
Data Source
AI summary
A semiconductor device includes a lead frame; a semiconductor chip mounted on the lead frame; and an encapsulation resin, wherein a convexo-concave portion including a plurality of concave portions is provided at a covered portion of the lead frame that is covered by the encapsulation resin, wherein the planer shape of each of the concave portions is a circle, the diameter of which is greater than or equal to 0.020 mm and less than or equal to 0.060 mm, or a polygon, the diameter of whose circumcircle is greater than or equal to 0.020 mm and less than or equal to 0.060 mm, and wherein a ratio S/S0 is greater than or equal to 1.7 where “S” is a surface area of the convexo-concave portion that is formed at a flat surface whose surface area is “S0”.